Humidity-conditioning construction materials are fabricated from porous materials, and therefore have a multitude of pores in their surfaces, and because these pores exhibit moisture adsorption and desorption properties, these construction materials have the ability to control the humidity within a target space such as an indoor room.
Under the humidity-conditioning construction material certification system, humidity-conditioning construction materials which satisfy certain humidity-conditioning properties and other conditions prescribed in humidity-conditioning construction material standards (Non-Patent Document 1) can be registered with the Japan Construction Material & Housing Equipment Industries Federation, and a special humidity-conditioning construction material mark can be displayed on registered humidity-conditioning construction materials as a guarantee of quality. Within these humidity-conditioning construction material standards, the registration conditions relating to the humidity-conditioning properties require that the material clears prescribed levels for the amount of moisture adsorption and desorption (JIS A 1470-1:2002, Determination of water vapor adsorption/desorption properties for building materials—Part 1: Response to humidity variation—method for testing water vapor adsorption/desorption upon humidity variation) and the equilibrium moisture content (namely, the moisture content gradient and the average equilibrium moisture content) (JIS A 1475:2004, Method of test for hygroscopic sorption properties of building materials).
Further, in humidity-conditioning performance evaluation standards for humidity-conditioning construction materials compiled in March 2006 by the Humidity-Conditioning Construction Materials Performance Evaluation Committee (Non-Patent Document 2), humidity-conditioning construction materials are classified into three grades shown below in Table 1 on the basis of the aforementioned amount of moisture adsorption and desorption and the equilibrium moisture content. Grade 1 describes a material that satisfies the minimum level of performance required for a humidity-conditioning construction material, grade 3 describes a material having excellent performance as a humidity-conditioning construction material, and grade 2 describes a material having performance midway between grade 1 and grade 3. These humidity-conditioning performance evaluation standards for humidity-conditioning construction materials are listed on the website of the Japan Testing Center for Construction Materials (http://www.jtccm.or.jp/main_services/seino/seino_jigyou_cyositu.html). In the case of the moisture adsorption and desorption properties, the standards stipulate that the amount of moisture adsorption at a relative humidity of 50 to 75% should exceed the numerical value shown below in Table 1, and the amount of moisture desorption after 12 hours should be about 70% or more of the amount of moisture adsorption over 12 hours, whereas in the case of the equilibrium moisture content, the standards stipulate that the value for the equilibrium moisture content in the moisture adsorption process (the moisture content mass by volume) should exceed the numerical value shown below in Table 1.
TABLE 1JIS A 1470-1 (Amount of moisture adsorption g/m2)Amount ofmoisture adsorption3 hours6 hours12 hoursGrade 3365071Grade 2253550Grade 1152029JIS A 1475 (Moisture content gradient Δψ (kg/m3/%),average equilibrium moisture content ψ (kg/m3))EquilibriumMoistureAveragemoisturecontentequilibriumcontentgradientmoisture contentGrade 30.418Grade 20.2611Grade 10.125(Note)Average equilibrium moisture content describes the value at a relative humidity of 55%
Known humidity-conditioning construction materials include materials fabricated from all manner of porous materials, and examples of humidity-conditioning construction materials containing an unexpanded vermiculite blended with calcium silicate include MOISS (a product name) manufactured by Mitsubishi Materials Kenzai Corporation, SARARIAET (a product name) manufactured by Daiken Corporation, ECOCARAT (a product name) manufactured by LIXIL Corporation (Inax), AG PLUS (a product name) manufactured by Nagoya Mosaic-Tile Co., Ltd., GAUDIA (a product name) manufactured by Sekisui Board Co., Ltd., and MONSIEUR (a product name) manufactured by Nikko Company.
In those cases where a humidity-conditioning construction material is used as an interior material, it is desirable that the surface of the humidity-conditioning construction material is decorated to enhance the decorative design characteristics, and a number of methods for decorating humidity-conditioning construction materials have already been proposed.
JP 2003-146775 A (Patent Document 1) discloses a technique for obtaining a construction material with excellent design characteristics by subjecting the surface of a humidity-conditioning construction material obtained by blending an unexpanded vermiculite with calcium silicate to a baking treatment.
JP 2011-26871 A (Patent Document 2) discloses a technique for decorating the surface of a humidity-conditioning construction material by using an inkjet recording device and an ultraviolet-curable ink to form an image on the surface of the material.